diff --git a/classes/csv_test.go b/classes/csv_test.go
new file mode 100644
index 0000000..2deca90
--- /dev/null
+++ b/classes/csv_test.go
@@ -0,0 +1,118 @@
+package classes
+
+import (
+	"errors"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// TestCSV: the export writes a BOM, the delimiter and escaped formula
+// cells; the import strips the BOM, detects or takes the delimiter, reads
+// quoting, unescapes formula cells and refuses what is not CSV.
+func TestCSV(t *testing.T) {
+	header := []string{"source", "target", "note"}
+	rows := [][]string{
+		{"/a", "/b", "plain"},
+		{"/ł", "/ż", "zażółć; gęślą, jaźń"},
+		{"/q", "/r", `she said "hi"` + "\nnext line"},
+		{"/f", "/g", "=HYPERLINK(\"x\")"},
+		{"/p", "/s", "+1"},
+		{"/m", "/n", "-1"},
+		{"/at", "/x", "@SUM(A1)"},
+		{"/tab", "/x", "\tlead"},
+		{"/cr", "/x", "\rlead"},
+		{"/ok", "/x", "a=b"},
+	}
+
+	t.Run("round trip with each delimiter", func(t *testing.T) {
+		for _, delim := range []string{",", ";", ""} {
+			out, err := WriteCSV(header, rows, delim)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !strings.HasPrefix(out, BOM) {
+				t.Fatalf("%q: no BOM", delim)
+			}
+			sep := ","
+			if delim == ";" {
+				sep = ";"
+			}
+			if !strings.HasPrefix(strings.TrimPrefix(out, BOM), strings.Join(header, sep)+"\n") {
+				t.Fatalf("%q: header line %q", delim, strings.SplitN(out, "\n", 2)[0])
+			}
+			gotHeader, got, err := ReadCSV(out, delim)
+			if err != nil || !reflect.DeepEqual(gotHeader, header) || len(got) != len(rows) {
+				t.Fatalf("%q: ReadCSV = %v, %d rows, %v", delim, gotHeader, len(got), err)
+			}
+			for i, row := range rows {
+				// Escaped cells keep their leading tab or CR: the apostrophe
+				// protects them from the import's trimming.
+				for j, col := range header {
+					if want := row[j]; got[i].Fields[col] != want {
+						t.Fatalf("%q row %d %s = %q, want %q", delim, i, col, got[i].Fields[col], want)
+					}
+				}
+			}
+		}
+	})
+
+	t.Run("formula cells are escaped on export", func(t *testing.T) {
+		out, _ := WriteCSV([]string{"note"}, [][]string{{"=1+1"}, {"+x"}, {"-x"}, {"@x"}, {"a=b"}, {""}}, ",")
+		lines := strings.Split(strings.TrimPrefix(out, BOM), "\n")
+		if lines[1] != "'=1+1" || lines[2] != "'+x" || lines[3] != "'-x" || lines[4] != "'@x" || lines[5] != "a=b" {
+			t.Fatalf("export = %q", lines)
+		}
+		for in, want := range map[string]string{"'=x": "=x", "'+x": "+x", "'abc": "'abc", "''=x": "''=x", "plain": "plain", "'": "'"} {
+			if got := unescapeCell(in); got != want {
+				t.Errorf("unescapeCell(%q) = %q, want %q", in, got, want)
+			}
+		}
+	})
+
+	t.Run("delimiter detection and the setting", func(t *testing.T) {
+		if CSVDelimiter(";") != ';' || CSVDelimiter(" ; ") != ';' || CSVDelimiter(",") != ',' || CSVDelimiter("") != ',' || CSVDelimiter("|") != ',' {
+			t.Fatal("CSVDelimiter")
+		}
+		h, rows, err := ReadCSV("Source;Target\n/a;/b\n", "")
+		if err != nil || !reflect.DeepEqual(h, []string{"source", "target"}) || rows[0].Fields["target"] != "/b" {
+			t.Fatalf("detected ; = %v %+v %v", h, rows, err)
+		}
+		h, rows, err = ReadCSV(BOM+" SOURCE , Target \n/a,/b\n", "")
+		if err != nil || !reflect.DeepEqual(h, []string{"source", "target"}) || rows[0].Line != 2 {
+			t.Fatalf("detected , = %v %+v %v", h, rows, err)
+		}
+	})
+
+	t.Run("quoting, blank rows and extra cells", func(t *testing.T) {
+		data := "source,target,note\n\"/a,1\",\"/b\"\"x\",\"two\nlines\"\n,,\n\n/c,/d,n,extra\n"
+		_, rows, err := ReadCSV(data, ",")
+		if err != nil || len(rows) != 2 {
+			t.Fatalf("rows = %+v, %v", rows, err)
+		}
+		if rows[0].Fields["source"] != "/a,1" || rows[0].Fields["target"] != `/b"x` || rows[0].Fields["note"] != "two\nlines" || rows[0].Line != 2 {
+			t.Fatalf("quoted row = %+v", rows[0])
+		}
+		if rows[1].Fields["source"] != "/c" || len(rows[1].Fields) != 3 || rows[1].Line != 6 {
+			t.Fatalf("row with an extra cell = %+v", rows[1])
+		}
+	})
+
+	t.Run("unreadable files", func(t *testing.T) {
+		for name, data := range map[string]string{
+			"empty":               "",
+			"a BOM only":          BOM,
+			"blank":               " \n\t\n",
+			"a bare quote":        "source,target\n\"/a,/b\n",
+			"the wrong delimiter": "source;target\n/a;/b\n",
+		} {
+			delim := ""
+			if name == "the wrong delimiter" {
+				delim = ","
+			}
+			if _, _, err := ReadCSV(data, delim); !errors.Is(err, ErrUnreadable) {
+				t.Errorf("%s: err = %v", name, err)
+			}
+		}
+	})
+}
diff --git a/classes/helpers_test.go b/classes/helpers_test.go
new file mode 100644
index 0000000..4a2976d
--- /dev/null
+++ b/classes/helpers_test.go
@@ -0,0 +1,134 @@
+package classes
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"gorm.io/driver/postgres"
+	"gorm.io/gorm"
+	"gorm.io/gorm/logger"
+
+	"git.golem15.com/golem15/summercms/modules/backpack"
+	"git.golem15.com/golem15/summercms/modules/compass"
+	"git.golem15.com/golem15/summercms/modules/pact"
+	"git.golem15.com/golem15/summercms/modules/signpost"
+)
+
+// testService is a service over an application config without a database:
+// env is SUMMER_ENV, site the golem15.seo.site_url ("" leaves it unset),
+// environ more SUMMER_ variables.
+func testService(t *testing.T, env, site string, environ ...string) *Service {
+	t.Helper()
+	svc, _ := testApp(t, env, site, environ...)
+	return svc
+}
+
+func testApp(t *testing.T, env, site string, environ ...string) (*Service, *backpack.App) {
+	t.Helper()
+	dir := t.TempDir()
+	if err := os.WriteFile(filepath.Join(dir, "app.yaml"), []byte("name: seo-unit\nlocale: en\nfallback_locale: en\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	vars := append([]string{"SUMMER_ENV=" + env}, environ...)
+	if site != "" {
+		vars = append(vars, "SUMMER_GOLEM15__SEO__SITE_URL="+site)
+	}
+	cfg, err := compass.Open(compass.Options{Dir: dir, Environ: vars})
+	if err != nil {
+		t.Fatal(err)
+	}
+	app := backpack.New(cfg)
+	svc, err := NewService(app)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return svc, app
+}
+
+// testPage is a record of the pages content type (/pages/:slug): a path
+// may carry a /pl prefix; a published record is matched exactly on its own
+// slug in the path's locale and inexactly on another of its slugs; a draft
+// is never matched.
+type testPage struct {
+	id        string
+	slugs     map[string]string // locale -> slug
+	published bool
+}
+
+type typesPlugin struct{ types []pact.MenuItemType }
+
+func (typesPlugin) ID() string                           { return "acme.pages" }
+func (p typesPlugin) MenuItemTypes() []pact.MenuItemType { return p.types }
+
+func testPagesType(pages ...testPage) pact.MenuItemType {
+	find := func(slug string) (testPage, string, bool) {
+		for _, p := range pages {
+			for locale, s := range p.slugs {
+				if s == slug {
+					return p, locale, true
+				}
+			}
+		}
+		return testPage{}, "", false
+	}
+	return pact.MenuItemType{
+		Key: "acme-page", DefaultPattern: "/pages/:slug",
+		Resolve: func(context.Context, pact.MenuItemResolve) (*pact.ResolvedMenuItem, error) { return nil, nil },
+		Content: &pact.ContentDescriptor{
+			Model: "acme_pages", Controller: "acme.pages.pages",
+			Describe: func(_ context.Context, in pact.ContentDescribe) (*pact.ContentRecord, error) {
+				for _, p := range pages {
+					if p.id == in.ID {
+						rec := &pact.ContentRecord{ID: p.id, Published: p.published}
+						for locale, slug := range p.slugs {
+							rec.Locales = append(rec.Locales, pact.ContentLocale{Locale: locale, URL: "/pages/" + slug, Title: "Page " + p.id})
+						}
+						return rec, nil
+					}
+				}
+				return nil, nil
+			},
+			Match: func(_ context.Context, in pact.ContentMatch) (*pact.ContentMatchResult, error) {
+				locale, path := "en", in.Path
+				if rest, ok := strings.CutPrefix(path, "/pl/"); ok {
+					locale, path = "pl", "/"+rest
+				}
+				values, ok := signpost.MatchPattern(in.Pattern, path)
+				if !ok {
+					return nil, nil
+				}
+				p, own, ok := find(values["slug"])
+				if !ok || !p.published {
+					return nil, nil
+				}
+				return &pact.ContentMatchResult{ID: p.id, Locale: locale, Exact: own == locale}, nil
+			},
+		},
+	}
+}
+
+// testServiceWithPages is testService with the pages content type
+// registered in signpost.
+func testServiceWithPages(t *testing.T, site string, pages ...testPage) *Service {
+	t.Helper()
+	svc, app := testApp(t, "production", site)
+	if err := signpost.Activate(app, []typesPlugin{{types: []pact.MenuItemType{testPagesType(pages...)}}}); err != nil {
+		t.Fatal(err)
+	}
+	return svc
+}
+
+// dryDB is a Postgres-dialect GORM handle that never connects: every query
+// is built and not run, so reads find no rows.
+func dryDB(t *testing.T) *gorm.DB {
+	t.Helper()
+	db, err := gorm.Open(postgres.New(postgres.Config{DSN: "host=127.0.0.1 port=1 user=seo dbname=seo sslmode=disable"}),
+		&gorm.Config{DryRun: true, DisableAutomaticPing: true, Logger: logger.Discard})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return db
+}
diff --git a/classes/issues_test.go b/classes/issues_test.go
new file mode 100644
index 0000000..10e88cf
--- /dev/null
+++ b/classes/issues_test.go
@@ -0,0 +1,149 @@
+package classes
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"reflect"
+	"testing"
+
+	"git.golem15.com/golem15/sm-seo-plugin/models"
+)
+
+// TestIssues: each kind of the CMS-data issue report from loaded data
+// (the database reads of Issues are covered by TestIssues in the plugin
+// package).
+func TestIssues(t *testing.T) {
+	svc := testServiceWithPages(t, "https://example.test",
+		testPage{id: "1", slugs: map[string]string{"en": "a"}, published: true},
+		testPage{id: "2", slugs: map[string]string{"en": "b"}, published: true},
+	)
+	entry := func(url, locale, title, desc string) models.Entry {
+		return models.Entry{URL: url, Locale: locale, EffectiveTitle: title, EffectiveDescription: desc}
+	}
+	canonicals := map[string][2]string{
+		"/noindexed": {IssueCanonicalNoindex, ""},
+		"/moved":     {IssueCanonicalRedirected, "/pages/a"},
+	}
+	canonical := func(_ context.Context, value string) (string, string, error) {
+		if value == "/boom" {
+			return "", "", errors.New("resolver down")
+		}
+		got := canonicals[value]
+		return got[0], got[1], nil
+	}
+	data := issueData{
+		locale: "en",
+		entries: []models.Entry{
+			func() models.Entry {
+				e := entry("/pages/a", "en", "Same Title", "First")
+				e.Canonical = "/moved"
+				return e
+			}(),
+			entry("/pages/b", "en", "same title ", ""),
+			entry("/pages/c", "en", "", "Shared description"),
+			entry("/pages/c", "pl", "Same Title", "Shared description"),
+			entry("/pages/d", "en", "Unique", "shared DESCRIPTION"),
+		},
+		rules: []models.Rule{
+			{ID: 7, URL: "/pages/a", Match: models.MatchExact, Robots: "noindex"},
+			{ID: 8, URL: "/landing", Match: models.MatchExact, Title: "Unique", Canonical: "/noindexed"},
+			{ID: 9, URL: "/pages/*", Match: models.MatchPattern, Title: "Same Title"},
+			{ID: 10, URL: "/pages/b?x=1", Match: models.MatchExact, Title: "Query rule"},
+			{ID: 11, URL: "/pages/b", Match: models.MatchExact},
+		},
+		redirects: []models.Redirect{rd(1, "/old1", "/old2"), rd(2, "/old2", "/pages/a"), rd(3, "/direct", "/pages/a")},
+		robots:    models.Robots{Content: "User-agent: *\nDisallow: /pages/a\n"},
+		noindex:   []string{"/pages/a", "/landing"},
+	}
+	issues, err := svc.issuesOf(t.Context(), data, canonical)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := map[string]Issue{}
+	var order []string
+	for _, is := range issues {
+		key := is.Kind + " " + is.URL + " " + is.Locale
+		if _, dup := got[key]; dup {
+			t.Fatalf("issue listed twice: %s", key)
+		}
+		got[key] = is
+		order = append(order, key)
+	}
+	want := []string{
+		"canonical_noindex /landing ",
+		"canonical_redirected /pages/a en",
+		"duplicate_description /pages/c en",
+		"duplicate_description /pages/d en",
+		"duplicate_title /landing ",
+		"duplicate_title /pages/a en",
+		"duplicate_title /pages/b en",
+		"duplicate_title /pages/d en",
+		"missing_description /pages/b en",
+		"missing_title /pages/c en",
+		"noindex_blocked /pages/a ",
+		"redirect_chain /old1 ",
+		"rule_overrides_record /pages/a en",
+	}
+	if !reflect.DeepEqual(order, want) {
+		t.Fatalf("issues (sorted by kind, url, locale):\n%v\nwant\n%v", order, want)
+	}
+	tools := map[string]string{
+		"canonical_noindex /landing ": "seo_update_rule", "canonical_redirected /pages/a en": "seo_set_url_seo",
+		"missing_title /pages/c en": "seo_set_url_seo", "noindex_blocked /pages/a ": "seo_update_robots",
+		"redirect_chain /old1 ": "seo_update_redirect", "rule_overrides_record /pages/a en": "seo_update_rule",
+	}
+	for key, tool := range tools {
+		if got[key].Tool != tool {
+			t.Errorf("%s tool = %s, want %s", key, got[key].Tool, tool)
+		}
+	}
+	if d := got["duplicate_title /pages/a en"].Details; d["value"] != "same title" || fmt.Sprint(d["also"]) != "[/pages/b]" {
+		t.Errorf("duplicate_title details = %v", d)
+	}
+	if d := got["duplicate_title /landing "].Details; fmt.Sprint(d["also"]) != "[/pages/d]" {
+		t.Errorf("a rule's title joins the default locale's duplicates: %v", d)
+	}
+	if d := got["rule_overrides_record /pages/a en"].Details; d["rule_id"] != uint(7) || d["type"] != "acme-page" || d["id"] != "1" || fmt.Sprint(d["fields"]) != "[robots]" {
+		t.Errorf("rule_overrides_record details = %v", d)
+	}
+	if d := got["redirect_chain /old1 "].Details; d["hops"] != 2 || d["final"] != "/pages/a" || fmt.Sprint(d["path"]) != "[/old1 /old2 /pages/a]" {
+		t.Errorf("redirect_chain details = %v", d)
+	}
+	if d := got["canonical_redirected /pages/a en"].Details; d["canonical"] != "/moved" || d["target"] != "/pages/a" {
+		t.Errorf("canonical_redirected details = %v", d)
+	}
+	if d := got["canonical_noindex /landing "].Details; d["rule_id"] != uint(8) || d["canonical"] != "/noindexed" {
+		t.Errorf("canonical_noindex details = %v", d)
+	}
+
+	t.Run("a clean site has no issues", func(t *testing.T) {
+		clean := issueData{locale: "en", entries: []models.Entry{entry("/pages/a", "en", "A", "About A"), entry("/pages/b", "en", "B", "About B")}}
+		if issues, err := svc.issuesOf(t.Context(), clean, canonical); err != nil || len(issues) != 0 {
+			t.Fatalf("issues = %+v, %v", issues, err)
+		}
+	})
+
+	t.Run("the same text in two locales is not a duplicate", func(t *testing.T) {
+		two := issueData{locale: "en", entries: []models.Entry{entry("/pages/a", "en", "Name", "Text"), entry("/pl/pages/a", "pl", "Name", "Text")}}
+		if issues, _ := svc.issuesOf(t.Context(), two, canonical); len(issues) != 0 {
+			t.Fatalf("issues = %+v", issues)
+		}
+	})
+
+	t.Run("a canonical check that fails stops the report", func(t *testing.T) {
+		broken := issueData{locale: "en", entries: []models.Entry{func() models.Entry { e := entry("/pages/a", "en", "A", "B"); e.Canonical = "/boom"; return e }()}}
+		if _, err := svc.issuesOf(t.Context(), broken, canonical); err == nil {
+			t.Fatal("the resolver error was dropped")
+		}
+	})
+
+	t.Run("canonicals on other sites and empty canonicals are not checked", func(t *testing.T) {
+		for _, value := range []string{"", "   ", "https://other.test/a"} {
+			kind, target, err := svc.canonicalProblem(t.Context(), value)
+			if kind != "" || target != "" || err != nil {
+				t.Errorf("canonicalProblem(%q) = %q %q %v", value, kind, target, err)
+			}
+		}
+	})
+}
diff --git a/classes/normalize_test.go b/classes/normalize_test.go
new file mode 100644
index 0000000..ddae863
--- /dev/null
+++ b/classes/normalize_test.go
@@ -0,0 +1,121 @@
+package classes
+
+import (
+	"net/url"
+	"testing"
+
+	"git.golem15.com/golem15/sm-seo-plugin/models"
+)
+
+// TestNormalizeMatrix: every combination of the address rules on every
+// input form reaches its final address in one hop (normalising the result
+// changes nothing), never touches the query, keeps the root and does not
+// modify its input.
+func TestNormalizeMatrix(t *testing.T) {
+	inputs := []string{
+		"/", "/a", "/a/", "/A/b", "//a//b/", "/a/index.html", "/A/Index.PHP", "/index.htm",
+		"/sitemap.xml", "/files/Doc.PDF/", "/%C5%81%C3%B3d%C5%BA/Abc/", "/a?Page=2&x=Y", "/a#frag",
+		"http://example.test", "http://example.test/A//B/", "https://www.example.test/a/index.html?q=1",
+		"https://WWW.Example.Test/Blog/", "http://www.example.test/",
+	}
+	var all []NormalizeOptions
+	for _, host := range []string{models.HostKeep, models.HostWWW, models.HostBare} {
+		for _, slash := range []string{models.SlashKeep, models.SlashAdd, models.SlashDrop} {
+			for _, lower := range []bool{false, true} {
+				all = append(all, NormalizeOptions{Host: host, Slash: slash, Lowercase: lower})
+			}
+		}
+	}
+	for _, opts := range all {
+		for _, in := range inputs {
+			u, err := url.Parse(in)
+			if err != nil {
+				t.Fatal(err)
+			}
+			before := *u
+			once, _ := Normalize(u, opts)
+			if *u != before {
+				t.Fatalf("%+v: Normalize(%s) modified its input", opts, in)
+			}
+			twice, changed := Normalize(once, opts)
+			if changed || twice.String() != once.String() {
+				t.Fatalf("%+v: %s -> %s -> %s (changed %v): not one hop", opts, in, once, twice, changed)
+			}
+			if once.RawQuery != u.RawQuery {
+				t.Fatalf("%+v: %s: query %q became %q", opts, in, u.RawQuery, once.RawQuery)
+			}
+			if once.Fragment != "" {
+				t.Fatalf("%+v: %s kept its fragment", opts, in)
+			}
+			if once.Host != "" && once.Scheme != "https" {
+				t.Fatalf("%+v: %s scheme %s", opts, in, once.Scheme)
+			}
+			if u.Path == "/" && once.Path != "/" {
+				t.Fatalf("%+v: the root became %s", opts, once.Path)
+			}
+		}
+	}
+}
+
+func TestNormalizeMatrixExpectations(t *testing.T) {
+	for _, tc := range []struct {
+		in   string
+		opts NormalizeOptions
+		want string
+	}{
+		{"/A//B/index.html", NormalizeOptions{Host: models.HostKeep, Slash: models.SlashKeep}, "/A/B"},
+		{"/A//B/index.html", NormalizeOptions{Slash: models.SlashAdd, Lowercase: true}, "/a/b/"},
+		{"/a/b///", NormalizeOptions{Slash: models.SlashDrop}, "/a/b"},
+		{"/a/b///", NormalizeOptions{Slash: models.SlashKeep}, "/a/b/"},
+		{"/report.PDF", NormalizeOptions{Slash: models.SlashAdd, Lowercase: true}, "/report.pdf"},
+		{"/v1.2/page", NormalizeOptions{Slash: models.SlashAdd}, "/v1.2/page/"},
+		{"http://EXAMPLE.test/a", NormalizeOptions{Host: models.HostKeep}, "https://example.test/a"},
+		{"http://www.example.test/a/", NormalizeOptions{Host: models.HostBare, Slash: models.SlashDrop}, "https://example.test/a"},
+		{"https://example.test", NormalizeOptions{Host: models.HostWWW, Slash: models.SlashAdd}, "https://www.example.test/"},
+		{"/%c5%81/%C5%82X", NormalizeOptions{Lowercase: true}, "/%C5%81/%C5%82x"},
+	} {
+		u, _ := url.Parse(tc.in)
+		got, _ := Normalize(u, tc.opts)
+		if got.String() != tc.want {
+			t.Errorf("Normalize(%s, %+v) = %s, want %s", tc.in, tc.opts, got, tc.want)
+		}
+	}
+	if got, changed := Normalize(nil, NormalizeOptions{}); got != nil || changed {
+		t.Fatal("Normalize(nil) answered a URL")
+	}
+	if got := NormalizeOptionsOf(models.Settings{URLHost: models.HostWWW, URLSlash: models.SlashAdd, URLLowercase: true}); got != (NormalizeOptions{Host: models.HostWWW, Slash: models.SlashAdd, Lowercase: true}) {
+		t.Fatalf("NormalizeOptionsOf = %+v", got)
+	}
+}
+
+func TestNormalizeHelpers(t *testing.T) {
+	for in, want := range map[string]string{"/": "/", "//": "/", "/a//b": "/a/b", "///a///": "/a/", "/a/b": "/a/b"} {
+		if got := collapseSlashes(in); got != want {
+			t.Errorf("collapseSlashes(%q) = %q", in, got)
+		}
+	}
+	if got := lowerASCII("/ŁÓDŹ/ABC-z"); got != "/ŁÓdŹ/abc-z" {
+		t.Errorf("lowerASCII = %q", got)
+	}
+	for in, want := range map[string]string{"/a/b.c": "b.c", "/a/": "", "x": "x", "/": ""} {
+		if got := lastSegment(in); got != want {
+			t.Errorf("lastSegment(%q) = %q", in, got)
+		}
+	}
+	for _, tc := range []struct {
+		site, host string
+		same       bool
+	}{
+		{"https://example.test", "example.test", true},
+		{"https://example.test", "WWW.example.test", true},
+		{"https://www.example.test", "example.test", true},
+		{"https://example.test", "evil.test", false},
+		{"https://example.test", "", false},
+		{"", "example.test", false},
+		{"https://example.test", "example.test.evil", false},
+	} {
+		if got := sameSite(tc.site, tc.host); got != tc.same {
+			t.Errorf("sameSite(%q, %q) = %v", tc.site, tc.host, got)
+		}
+	}
+}
diff --git a/classes/owner_test.go b/classes/owner_test.go
new file mode 100644
index 0000000..5933f42
--- /dev/null
+++ b/classes/owner_test.go
@@ -0,0 +1,74 @@
+package classes
+
+import (
+	"errors"
+	"testing"
+)
+
+// TestOwnerResolution: a URL's SEO belongs to the record behind it in the
+// matched locale when the URL is the record's exact address without a
+// query; otherwise, and with force_rule, to an exact URL rule on the
+// normalised address (D-11, P-25).
+func TestOwnerResolution(t *testing.T) {
+	svc := testServiceWithPages(t, "https://example.test",
+		testPage{id: "1", slugs: map[string]string{"en": "about", "pl": "o-nas"}, published: true},
+		testPage{id: "2", slugs: map[string]string{"en": "draft"}, published: false},
+	)
+	db := dryDB(t)
+	for _, tc := range []struct {
+		name, url string
+		force     bool
+		writtenTo string
+		id        string
+		locale    string
+		address   string
+		published bool
+	}{
+		{"the record's own address", "/pages/about", false, WrittenToRecord, "1", "en", "/pages/about", true},
+		{"an absolute URL of the site", "https://example.test/pages/about", false, WrittenToRecord, "1", "en", "/pages/about", true},
+		{"the locale prefix names the locale", "/pl/pages/o-nas", false, WrittenToRecord, "1", "pl", "/pl/pages/o-nas", true},
+		{"a trailing slash still finds the record", "/pages/about/", false, WrittenToRecord, "1", "en", "/pages/about/", true},
+		{"double slashes are normalised first", "//pages//about", false, "", "", "", "", false},
+		{"force_rule writes a rule on the record's address", "/pages/about", true, WrittenToRule, "", "", "/pages/about", false},
+		{"a query makes it a rule", "/pages/about?page=2", false, WrittenToRule, "", "", "/pages/about?page=2", false},
+		{"another locale's slug is not the record's address", "/pages/o-nas", false, WrittenToRule, "", "", "/pages/o-nas", false},
+		{"a draft is not matched", "/pages/draft", false, WrittenToRule, "", "", "/pages/draft", false},
+		{"an address without a record", "/landing", false, WrittenToRule, "", "", "/landing", false},
+		{"the home page", "/", false, WrittenToRule, "", "", "/", false},
+		{"an index file is normalised away", "/pages/about/index.html", false, WrittenToRecord, "1", "en", "/pages/about", true},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			owner, typ, err := svc.FindOwner(t.Context(), db, tc.url, tc.force)
+			if tc.writtenTo == "" {
+				if !errors.Is(err, ErrBadURL) {
+					t.Fatalf("FindOwner(%q) = %+v, %v; want ErrBadURL", tc.url, owner, err)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatal(err)
+			}
+			if owner.WrittenTo != tc.writtenTo || owner.ID != tc.id || owner.Locale != tc.locale || owner.URL != tc.address || owner.Published != tc.published {
+				t.Fatalf("FindOwner(%q) = %+v", tc.url, owner)
+			}
+			if tc.writtenTo == WrittenToRecord && (owner.Type != "acme-page" || typ.Key != "acme-page") {
+				t.Fatalf("type = %q %q", owner.Type, typ.Key)
+			}
+			if tc.writtenTo == WrittenToRule && (owner.Type != "" || typ.Key != "" || owner.RuleID != 0) {
+				t.Fatalf("rule owner = %+v (%s)", owner, typ.Key)
+			}
+		})
+	}
+	for _, bad := range []string{"", "pages/about", "ftp://example.test/a", "javascript:alert(1)"} {
+		if _, _, err := svc.FindOwner(t.Context(), db, bad, false); !errors.Is(err, ErrBadURL) {
+			t.Errorf("FindOwner(%q) = %v, want ErrBadURL", bad, err)
+		}
+	}
+
+	t.Run("without a signpost registry every URL is a rule", func(t *testing.T) {
+		owner, _, err := testService(t, "production", "https://example.test").FindOwner(t.Context(), db, "/pages/about", false)
+		if err != nil || owner.WrittenTo != WrittenToRule || owner.URL != "/pages/about" {
+			t.Fatalf("owner = %+v, %v", owner, err)
+		}
+	})
+}
diff --git a/classes/redirect_graph_test.go b/classes/redirect_graph_test.go
new file mode 100644
index 0000000..0b5e2cb
--- /dev/null
+++ b/classes/redirect_graph_test.go
@@ -0,0 +1,184 @@
+package classes
+
+import (
+	"strconv"
+	"strings"
+	"testing"
+
+	"git.golem15.com/golem15/sm-seo-plugin/models"
+)
+
+// rd is an exact 301 rule with defaults.
+func rd(id uint, source, target string) models.Redirect {
+	r := models.NewRedirect()
+	r.ID, r.Source, r.Target = id, source, target
+	return r
+}
+
+func rdMatch(id uint, match, source, target string) models.Redirect {
+	r := rd(id, source, target)
+	r.Match = match
+	return r
+}
+
+const rdSite = "https://example.test"
+
+// TestRedirectGraph: the redirect graph rules of D-18/D-19 over rule lists
+// (the database writes of AddressChanged are covered by TestSlugChange301
+// and TestAddressChangeFromEvent in the plugin package).
+func TestRedirectGraph(t *testing.T) {
+	t.Run("a chain A to B to C is a chain notice from A to C", func(t *testing.T) {
+		stored := []models.Redirect{rd(1, "/b", "/c")}
+		check, err := checkRedirectRules(rdSite, stored, rd(0, "/a", "/b"))
+		if err != nil || check.Loop || !check.Chain || check.Hops != 2 || check.Source != "/a" || check.Final != "/c" || check.PathText() != "/a → /b → /c" {
+			t.Fatalf("check = %+v, %v", check, err)
+		}
+		notice := ChainNotice(check)
+		if len(notice) != 1 || notice[0].Params["count"] != "2" || notice[0].Params["final"] != "/c" || notice[0].Params["source"] != "/a" {
+			t.Fatalf("notice = %+v", notice)
+		}
+	})
+
+	t.Run("a rule that another rule leads into is the second hop of a chain", func(t *testing.T) {
+		stored := []models.Redirect{rd(1, "/a", "/b")}
+		check, err := checkRedirectRules(rdSite, stored, rd(0, "/b", "/c"))
+		if err != nil || !check.Chain || check.Hops != 2 || check.Source != "/a" || check.Final != "/c" {
+			t.Fatalf("check = %+v, %v", check, err)
+		}
+	})
+
+	t.Run("the flattened graph A to C, B to C is one hop each", func(t *testing.T) {
+		set := NewRedirectSet([]models.Redirect{rd(1, "/a", "/c"), rd(2, "/b", "/c")})
+		for _, from := range []string{"/a", "/b"} {
+			ch, err := set.Follow(rdSite, from, "", MaxRedirectHops)
+			if err != nil || len(ch.Hops) != 1 || ch.Final != "/c" || ch.Loop {
+				t.Fatalf("%s: chain = %+v, %v", from, ch, err)
+			}
+		}
+		for _, r := range []models.Redirect{rd(1, "/a", "/c"), rd(2, "/b", "/c")} {
+			others := []models.Redirect{rd(1, "/a", "/c"), rd(2, "/b", "/c")}
+			if check, err := checkRedirectRules(rdSite, others, r); err != nil || check.Chain || check.Loop {
+				t.Fatalf("%s: check = %+v, %v", r.Source, check, err)
+			}
+		}
+	})
+
+	t.Run("back and forth A to B to A to C ends as A to C and B to C", func(t *testing.T) {
+		// After A→B, B→A (the address returned) and then A→C, the graph
+		// AddressChanged leaves is A→C and B→C: no rule shadows the live
+		// address and every old address reaches C in one hop.
+		set := NewRedirectSet([]models.Redirect{rd(1, "/a", "/c"), rd(2, "/b", "/c")})
+		for _, from := range []string{"/a", "/b"} {
+			if ch, _ := set.Follow(rdSite, from, "", MaxRedirectHops); len(ch.Hops) != 1 || ch.Final != "/c" {
+				t.Fatalf("%s: chain = %+v", from, ch)
+			}
+		}
+		if _, ok, _ := set.Match("/c", ""); ok {
+			t.Fatal("the live address is shadowed")
+		}
+		// Back and forth without the cleanup would be a loop.
+		check, err := checkRedirectRules(rdSite, []models.Redirect{rd(1, "/a", "/b")}, rd(0, "/b", "/a"))
+		if err != nil || !check.Loop {
+			t.Fatalf("A→B then B→A = %+v, %v; want a loop", check, err)
+		}
+	})
+
+	loops := []struct {
+		name   string
+		stored []models.Redirect
+		rule   models.Redirect
+		path   string
+	}{
+		{"exact self loop", nil, rd(0, "/a", "/a"), "/a → /a"},
+		{"exact two-rule loop", []models.Redirect{rd(1, "/b", "/a")}, rd(0, "/a", "/b"), "/a → /b → /a"},
+		{"exact three-rule loop", []models.Redirect{rd(1, "/b", "/c"), rd(2, "/c", "/a")}, rd(0, "/a", "/b"), "/a → /b → /c → /a"},
+		{"exact loop through the site's absolute URL", []models.Redirect{rd(1, "/b", rdSite+"/a")}, rd(0, "/a", "/b"), "/a → /b → /a"},
+		{"exact loop through case and trailing slash", []models.Redirect{rd(1, "/b", "/A/")}, func() models.Redirect { r := rd(0, "/a", "/b"); r.IgnoreCase = true; return r }(), ""},
+		{"pattern probe loop", []models.Redirect{rd(1, "/new/seoprobe", "/old/x")}, rdMatch(0, models.RedirectPattern, "/old/*", "/new/*"), ""},
+		{"pattern onto itself", nil, rdMatch(0, models.RedirectPattern, "/docs/*", "/docs/*"), ""},
+		{"regex probe loop", []models.Redirect{rdMatch(1, models.RedirectPattern, "/b/*", "/a/*")}, rdMatch(0, models.RedirectRegex, `^/a/(\d+)$`, "/b/$1"), `^/a/(\d+)$ → /b/0 → /a/0`},
+		{"regex onto itself", nil, rdMatch(0, models.RedirectRegex, `^/x/([a-z]+)$`, "/x/$1"), ""},
+	}
+	for _, tc := range loops {
+		t.Run("loop refused: "+tc.name, func(t *testing.T) {
+			check, err := checkRedirectRules(rdSite, tc.stored, tc.rule)
+			if err != nil || !check.Loop {
+				t.Fatalf("check = %+v, %v; want a loop", check, err)
+			}
+			if tc.path != "" && check.PathText() != tc.path {
+				t.Fatalf("path = %q, want %q", check.PathText(), tc.path)
+			}
+			if msg := (&LoopError{Check: check}).Error(); !strings.Contains(msg, "loop") {
+				t.Fatalf("LoopError = %q", msg)
+			}
+		})
+	}
+
+	t.Run("a 410 rule ends every chain and is never a loop", func(t *testing.T) {
+		gone := rd(0, "/a", "")
+		gone.Status = models.Status410
+		if check, err := checkRedirectRules(rdSite, []models.Redirect{rd(1, "/b", "/a")}, gone); err != nil || check.Loop || check.Chain {
+			t.Fatalf("check = %+v, %v", check, err)
+		}
+		set := NewRedirectSet([]models.Redirect{rd(1, "/b", "/a"), func() models.Redirect { g := gone; g.ID = 2; return g }()})
+		ch, err := set.Follow(rdSite, "/b", "", MaxRedirectHops)
+		if err != nil || !ch.Gone || ch.Loop || len(ch.Hops) != 2 {
+			t.Fatalf("chain = %+v, %v", ch, err)
+		}
+	})
+
+	t.Run("an external target ends the chain", func(t *testing.T) {
+		set := NewRedirectSet([]models.Redirect{rd(1, "/a", "https://other.test/a"), rd(2, "/b", "/a")})
+		ch, err := set.Follow(rdSite, "/b", "", MaxRedirectHops)
+		if err != nil || ch.Loop || len(ch.Hops) != 2 || ch.Final != "https://other.test/a" {
+			t.Fatalf("chain = %+v, %v", ch, err)
+		}
+	})
+
+	t.Run("the runtime stops after 10 hops", func(t *testing.T) {
+		var rules []models.Redirect
+		for i := 0; i < 15; i++ {
+			rules = append(rules, rd(uint(i+1), "/p"+strconv.Itoa(i), "/p"+strconv.Itoa(i+1)))
+		}
+		set := NewRedirectSet(rules)
+		ch, err := set.Follow(rdSite, "/p0", "", MaxRedirectHops)
+		if err != nil || !ch.Loop || len(ch.Hops) != MaxRedirectHops || MaxRedirectHops != 10 {
+			t.Fatalf("chain = %d hops, loop %v, %v", len(ch.Hops), ch.Loop, err)
+		}
+		// Reaching the cap counts as a loop; a chain one hop shorter ends.
+		capped, _ := set.Follow(rdSite, "/p5", "", MaxRedirectHops)
+		if !capped.Loop || len(capped.Hops) != 10 {
+			t.Fatalf("ten hops: %d hops, loop %v", len(capped.Hops), capped.Loop)
+		}
+		short, err := set.Follow(rdSite, "/p6", "", MaxRedirectHops)
+		if err != nil || short.Loop || len(short.Hops) != 9 || short.Final != "/p15" {
+			t.Fatalf("nine hops: %d hops, loop %v, final %s", len(short.Hops), short.Loop, short.Final)
+		}
+		// A new rule that makes a chain longer than the cap is a loop.
+		check, err := checkRedirectRules(rdSite, rules[1:], rd(0, "/p0", "/p1"))
+		if err != nil || !check.Loop {
+			t.Fatalf("an 11-hop chain = %+v, %v; want refused", check, err)
+		}
+	})
+
+	t.Run("probes", func(t *testing.T) {
+		for _, tc := range []struct {
+			rule models.Redirect
+			path string
+			ok   bool
+		}{
+			{rd(0, "/a?x=1", "/b"), "/a", true},
+			{rdMatch(0, models.RedirectPattern, "/old/*/x", "/n"), "/old/seoprobe/x", true},
+			{rdMatch(0, models.RedirectRegex, `^/a/[0-9]{2}/(x|y)$`, "/n"), "/a/00/x", true},
+			{rdMatch(0, models.RedirectRegex, `^/a/\w+$`, "/n"), "/a/a", true},
+			{rdMatch(0, models.RedirectRegex, `^a$`, "/n"), "", false},
+			{rdMatch(0, models.RedirectRegex, `(`, "/n"), "", false},
+			{rdMatch(0, models.RedirectRegex, `^/a\?q$`, "/n"), "", false},
+		} {
+			path, _, ok := redirectProbe(tc.rule)
+			if ok != tc.ok || (ok && path != tc.path) {
+				t.Errorf("redirectProbe(%s %q) = %q %v, want %q %v", tc.rule.Match, tc.rule.Source, path, ok, tc.path, tc.ok)
+			}
+		}
+	})
+}
diff --git a/classes/resolver_test.go b/classes/resolver_test.go
new file mode 100644
index 0000000..e20d1f5
--- /dev/null
+++ b/classes/resolver_test.go
@@ -0,0 +1,160 @@
+package classes
+
+import (
+	"testing"
+
+	"git.golem15.com/golem15/sm-seo-plugin/models"
+)
+
+// layer is one layer of a value chain: its source and the value it holds
+// when present.
+type layer struct{ source, value string }
+
+// TestResolverPrecedence: every value chain of the resolver (P-14) with
+// each layer present and absent picks the first present layer and reports
+// its source; robots merge per directive; outside production the lock
+// wins; a draft is not found. The Postgres-backed answer with stored rules
+// and entries is TestResolverPrecedence in the plugin package.
+func TestResolverPrecedence(t *testing.T) {
+	chains := map[string][]layer{
+		// rule > record > type or general template > content > site name
+		"title": {{SourceRule, "Rule title"}, {SourceRecord, "Record title"}, {SourceTemplate, "Post | Site"}, {SourceContent, "Post"}, {SourceGlobal, "Site"}},
+		// rule > record > type template > content > default description
+		"description": {{SourceRule, "Rule desc"}, {SourceRecord, "Record desc"}, {SourceTemplate, "Template desc"}, {SourceContent, "Excerpt"}, {SourceGlobal, "Default desc"}},
+		// rule > record (else the address itself)
+		"canonical": {{SourceRule, "/rule"}, {SourceRecord, "/record"}},
+		// override rule > record > the effective title
+		"og_title": {{SourceRule, "OG rule"}, {SourceRecord, "OG record"}, {SourceTemplate, "Effective title"}},
+		// override rule > record > the effective description
+		"og_description": {{SourceRule, "OG rule"}, {SourceRecord, "OG record"}, {SourceContent, "Effective description"}},
+		// rule > record > content image > default social image
+		"og_image": {{SourceRule, "/r.png"}, {SourceRecord, "/e.png"}, {SourceContent, "/c.png"}, {SourceGlobal, "/d.png"}},
+	}
+	for name, chain := range chains {
+		t.Run(name, func(t *testing.T) {
+			for mask := 0; mask < 1<<len(chain); mask++ {
+				cands := make([]candidate, len(chain))
+				wantValue, wantSource := "", SourceDefault
+				for i, l := range chain {
+					if mask&(1<<i) != 0 {
+						cands[i] = candidate{"  " + l.value + " ", l.source}
+						if wantValue == "" {
+							wantValue, wantSource = l.value, l.source
+						}
+					} else {
+						cands[i] = candidate{" \t", l.source}
+					}
+				}
+				if value, source := pick(cands...); value != wantValue || source != wantSource {
+					t.Fatalf("layers %0*b: pick = %q from %s, want %q from %s", len(chain), mask, value, source, wantValue, wantSource)
+				}
+			}
+		})
+	}
+
+	t.Run("the first URL rule with a value wins", func(t *testing.T) {
+		rules := []models.Rule{{URL: "/a", Title: " "}, {URL: "/a*", Title: "Pattern"}, {URL: "/*", Title: "Wide"}}
+		if got := ruleValue(rules, "title"); got != "Pattern" {
+			t.Fatalf("ruleValue = %q", got)
+		}
+		if got := ruleValue(rules, "description"); got != "" {
+			t.Fatalf("ruleValue of an unset column = %q", got)
+		}
+	})
+
+	t.Run("robots per directive", func(t *testing.T) {
+		for _, tc := range []struct {
+			name   string
+			layers []robotsLayer
+			want   string
+			source string
+		}{
+			{"no layer: index, follow", nil, "index, follow", SourceDefault},
+			{"the rule decides", []robotsLayer{{"noindex", SourceRule}, {"index,nofollow", SourceRecord}}, "noindex, nofollow", SourceRule},
+			{"the record decides", []robotsLayer{{"", SourceRule}, {"noindex", SourceRecord}, {"index", SourceTemplate}}, "noindex, follow", SourceRecord},
+			{"never-indexed paths", []robotsLayer{{"", SourceRule}, {"", SourceRecord}, {"noindex,nofollow", SourceGlobal}}, "noindex, nofollow", SourceGlobal},
+			{"the type default", []robotsLayer{{"", SourceRule}, {"", SourceRecord}, {"noindex,max-snippet:20", SourceTemplate}}, "noindex, follow, max-snippet:20", SourceTemplate},
+			{"a layer without index does not decide", []robotsLayer{{"nofollow", SourceRule}, {"noarchive", SourceRecord}}, "index, nofollow, noarchive", SourceDefault},
+			{"directives merge across layers", []robotsLayer{{"max-snippet:5", SourceRule}, {"noindex,max-snippet:50,max-image-preview:large", SourceRecord}}, "noindex, follow, max-snippet:5, max-image-preview:large", SourceRecord},
+			{"a malformed layer is skipped", []robotsLayer{{"noindex,noindex", SourceRule}, {"noindex", SourceRecord}}, "noindex, follow", SourceRecord},
+		} {
+			t.Run(tc.name, func(t *testing.T) {
+				r, source := resolveRobots(tc.layers)
+				if r.Header() != tc.want || source != tc.source {
+					t.Fatalf("resolveRobots = %q from %s, want %q from %s", r.Header(), source, tc.want, tc.source)
+				}
+			})
+		}
+	})
+
+	pages := []testPage{
+		{id: "1", slugs: map[string]string{"en": "about"}, published: true},
+		{id: "2", slugs: map[string]string{"en": "draft"}, published: false},
+	}
+	db := dryDB(t)
+
+	t.Run("a published record without stored SEO", func(t *testing.T) {
+		svc := testServiceWithPages(t, "https://example.test", pages...)
+		res, err := svc.Resolver().Resolve(WithTx(t.Context(), db), "/pages/about")
+		if err != nil {
+			t.Fatal(err)
+		}
+		if res.Action != ActionOK || res.Status != 200 || res.Staging || res.TypeKey != "acme-page" || res.RecordID != "1" {
+			t.Fatalf("result = %+v", res)
+		}
+		seo := res.SEO
+		// The general template on the content title; no site name, so the
+		// separator is trimmed.
+		if seo.Title != "Page 1" || res.Sources["title"] != SourceTemplate {
+			t.Fatalf("title = %q from %s", seo.Title, res.Sources["title"])
+		}
+		if seo.Description != "" || res.Sources["description"] != SourceDefault {
+			t.Fatalf("description = %q from %s", seo.Description, res.Sources["description"])
+		}
+		if seo.Canonical != "https://example.test/pages/about" || res.Sources["canonical"] != SourceDefault {
+			t.Fatalf("canonical = %q from %s", seo.Canonical, res.Sources["canonical"])
+		}
+		if seo.Robots != "index, follow" || seo.XRobotsTag != "index, follow" || res.Sources["robots"] != SourceDefault {
+			t.Fatalf("robots = %q from %s", seo.Robots, res.Sources["robots"])
+		}
+		if seo.OG.Title != "Page 1" || res.Sources["og_title"] != SourceTemplate || seo.OG.URL != seo.Canonical || seo.Twitter.Card != "summary" {
+			t.Fatalf("social = %+v %v", seo.OG, res.Sources)
+		}
+	})
+
+	t.Run("the staging lock", func(t *testing.T) {
+		svc := testService(t, "staging", "https://example.test")
+		res, err := svc.Resolver().Resolve(WithTx(t.Context(), db), "/")
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !res.Staging || res.SEO.Robots != "noindex, nofollow" || res.SEO.XRobotsTag != "noindex, nofollow" || res.Sources["robots"] != SourceDefault {
+			t.Fatalf("staging = %v, robots %q from %s", res.Staging, res.SEO.Robots, res.Sources["robots"])
+		}
+		prod, err := testService(t, "production", "https://example.test").Resolver().Resolve(WithTx(t.Context(), db), "/")
+		if err != nil || prod.Staging || prod.SEO.Robots != "index, follow" {
+			t.Fatalf("production home = %+v, %v", prod, err)
+		}
+	})
+
+	t.Run("a draft is not found", func(t *testing.T) {
+		svc := testServiceWithPages(t, "https://example.test", pages...)
+		for _, path := range []string{"/pages/draft", "/pages/missing", "/elsewhere"} {
+			res, err := svc.Resolver().Resolve(WithTx(t.Context(), db), path)
+			if err != nil || res.Action != ActionNotFound || res.Status != 404 || res.SEO != nil {
+				t.Fatalf("%s = %+v, %v", path, res, err)
+			}
+		}
+		if res, err := svc.Resolver().Resolve(WithTx(t.Context(), db), "/"); err != nil || res.Action != ActionOK {
+			t.Fatalf("the home page without a record = %+v, %v", res, err)
+		}
+	})
+
+	t.Run("a record's address in another form moves in one hop", func(t *testing.T) {
+		svc := testServiceWithPages(t, "https://example.test", pages...)
+		res, err := svc.Resolver().Resolve(WithTx(t.Context(), db), "/pages//about/index.html")
+		if err != nil || res.Action != ActionRedirect || res.Status != 301 || res.Location != "https://example.test/pages/about" {
+			t.Fatalf("result = %+v, %v", res, err)
+		}
+	})
+}
diff --git a/classes/robots_test.go b/classes/robots_test.go
new file mode 100644
index 0000000..ad013eb
--- /dev/null
+++ b/classes/robots_test.go
@@ -0,0 +1,126 @@
+package classes
+
+import (
+	"strings"
+	"testing"
+
+	"git.golem15.com/golem15/sm-seo-plugin/models"
+)
+
+// TestRobotsMatcherGoogleExamples runs the tester on the examples of
+// Google's robots.txt documentation: the longest match wins, Allow wins a
+// tie, * matches any text, $ anchors the end, paths are case-sensitive,
+// and a group naming the agent replaces the * group.
+func TestRobotsMatcherGoogleExamples(t *testing.T) {
+	svc := testService(t, "production", "https://example.test")
+	for _, tc := range []struct {
+		name, file, agent, path string
+		allowed                 bool
+		rule                    string
+	}{
+		{"longest match: allow /p beats disallow /", "User-agent: *\nAllow: /p\nDisallow: /\n", "Googlebot", "/page", true, "Allow: /p"},
+		{"tie: allow wins", "User-agent: *\nAllow: /folder\nDisallow: /folder\n", "Googlebot", "/folder/page", true, "Allow: /folder"},
+		{"longer wildcard disallow beats allow", "User-agent: *\nAllow: /page\nDisallow: /*.htm\n", "Googlebot", "/page.htm", false, "Disallow: /*.htm"},
+		{"$ allows the root only", "User-agent: *\nAllow: /$\nDisallow: /\n", "Googlebot", "/", true, "Allow: /$"},
+		{"$ does not allow below the root", "User-agent: *\nAllow: /$\nDisallow: /\n", "Googlebot", "/page.htm", false, "Disallow: /"},
+		{"* and $: a .gif file", "User-agent: *\nDisallow: /*.gif$\n", "Googlebot", "/files/a.gif", false, "Disallow: /*.gif$"},
+		{"* and $: a .gif with a query is not the end", "User-agent: *\nDisallow: /*.gif$\n", "Googlebot", "/files/a.gif?x=1", true, ""},
+		{"a trailing * changes nothing", "User-agent: *\nDisallow: /fish*\n", "Googlebot", "/fish.html", false, "Disallow: /fish*"},
+		{"paths are case-sensitive", "User-agent: *\nDisallow: /fish\n", "Googlebot", "/Fish.asp", true, ""},
+		{"a prefix, not a word", "User-agent: *\nDisallow: /fish\n", "Googlebot", "/catfish", true, ""},
+		{"a prefix covers longer paths", "User-agent: *\nDisallow: /fish\n", "Googlebot", "/fishheads/yummy.html", false, "Disallow: /fish"},
+		{"a directory rule", "User-agent: *\nDisallow: /fish/\n", "Googlebot", "/fish", true, ""},
+		{"an empty Disallow allows everything", "User-agent: *\nDisallow:\n", "Googlebot", "/anything", true, "Disallow:"},
+		{"the agent's group replaces *", "User-agent: *\nDisallow: /\n\nUser-agent: Googlebot\nAllow: /\n", "Googlebot", "/x", true, "Allow: /"},
+		{"other agents keep the * group", "User-agent: *\nDisallow: /\n\nUser-agent: Googlebot\nAllow: /\n", "Bingbot", "/x", false, "Disallow: /"},
+		{"agent names ignore case", "User-agent: googlebot\nDisallow: /private\n", "Googlebot", "/private/a", false, "Disallow: /private"},
+		{"no rule matches", "User-agent: *\nDisallow: /admin\n", "Googlebot", "/blog", true, ""},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			got := svc.TestRobots(tc.file, nil, tc.agent, tc.path)
+			if got.Allowed != tc.allowed || got.Rule != tc.rule || got.Bot || got.Agent != tc.agent || got.Staging {
+				t.Fatalf("TestRobots(%q, %s) = %+v; want allowed %v by %q", tc.path, tc.agent, got, tc.allowed, tc.rule)
+			}
+			if tc.rule != "" && strings.Split(tc.file, "\n")[got.Line-1] != tc.rule {
+				t.Fatalf("line %d is not %q", got.Line, tc.rule)
+			}
+			if tc.rule == "" && got.Line != 0 {
+				t.Fatalf("line = %d without a matching rule", got.Line)
+			}
+		})
+	}
+}
+
+func TestRobotsBotSwitches(t *testing.T) {
+	svc := testService(t, "production", "https://example.test")
+	content := "User-agent: *\nDisallow: /admin\n"
+	off := models.BotSwitches{"GPTBot": false, "ClaudeBot": true}
+
+	got := svc.TestRobots(content, off, "GPTBot", "/blog")
+	if got.Allowed || !got.Bot || got.Rule != "Disallow: /" || got.Line < generatedStart(content) {
+		t.Fatalf("a switched-off bot = %+v", got)
+	}
+	if got := svc.TestRobots(content, off, "ClaudeBot", "/blog"); !got.Allowed || got.Bot {
+		t.Fatalf("a switched-on bot = %+v", got)
+	}
+	if got := svc.TestRobots(content, off, "ClaudeBot", "/admin/x"); got.Allowed || got.Bot || got.Rule != "Disallow: /admin" {
+		t.Fatalf("the editor's rule = %+v", got)
+	}
+	if got := testService(t, "staging", "https://example.test").TestRobots(content, nil, "Googlebot", "/blog"); !got.Staging || !got.Allowed {
+		t.Fatalf("outside production the tester tests the production file and says so: %+v", got)
+	}
+	if got := testService(t, "production", "").TestRobots(content, nil, "Googlebot", "/admin"); got.Allowed {
+		t.Fatalf("without a site URL = %+v", got)
+	}
+}
+
+func TestRobotsCompose(t *testing.T) {
+	sitemaps := []string{"https://example.test/sitemap.xml"}
+	for _, tc := range []struct {
+		name, content string
+		bots          models.BotSwitches
+		sitemaps      []string
+		want          string
+	}{
+		{"rules, a bot and a sitemap", "User-agent: *\r\nDisallow: /admin\r\n\r\n", models.BotSwitches{"CCBot": false}, sitemaps,
+			"User-agent: *\nDisallow: /admin\n\nUser-agent: CCBot\nDisallow: /\n\nSitemap: https://example.test/sitemap.xml\n"},
+		{"bots in list order", "", models.BotSwitches{"CCBot": false, "GPTBot": false, "OAI-SearchBot": true}, nil,
+			"User-agent: GPTBot\nDisallow: /\n\nUser-agent: CCBot\nDisallow: /\n"},
+		{"sitemaps only", "", nil, []string{"https://example.test/a.xml", "https://example.test/b.xml"},
+			"Sitemap: https://example.test/a.xml\nSitemap: https://example.test/b.xml\n"},
+		{"rules only", "User-agent: *\nDisallow:", nil, nil, "User-agent: *\nDisallow:\n"},
+		{"nothing", "  \n", nil, nil, ""},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := ComposeRobots(tc.content, tc.bots, tc.sitemaps); got != tc.want {
+				t.Fatalf("ComposeRobots = %q\nwant %q", got, tc.want)
+			}
+		})
+	}
+	for content, want := range map[string]int{"": 1, "a": 2, "a\nb\n\n": 3, "a\r\nb": 3} {
+		if got := generatedStart(content); got != want {
+			t.Errorf("generatedStart(%q) = %d, want %d", content, got, want)
+		}
+	}
+	for _, bot := range Bots {
+		if field := BotField(bot.Token); strings.ContainsAny(field, "-ABCDEFGHIJKLMNOPQRSTUVWXYZ") || !strings.HasPrefix(field, "bot_") {
+			t.Errorf("BotField(%s) = %s", bot.Token, field)
+		}
+		if got, ok := BotByToken(strings.ToLower(bot.Token)); !ok || got != bot {
+			t.Errorf("BotByToken(%s) = %+v %v", bot.Token, got, ok)
+		}
+	}
+	if _, ok := BotByToken("Googlebot"); ok {
+		t.Error("Googlebot is not an AI bot of the list")
+	}
+}
+
+func TestRobotsSitemapsConfig(t *testing.T) {
+	if got := testService(t, "production", "https://example.test").RobotsSitemaps(); len(got) != 1 || got[0] != "https://example.test/sitemap.xml" {
+		t.Fatalf("default = %v", got)
+	}
+	got := testService(t, "production", "https://example.test", "SUMMER_GOLEM15__SEO__ROBOTS_SITEMAPS=/a.xml, https://cdn.example.test/b.xml").RobotsSitemaps()
+	if strings.Join(got, " ") != "https://example.test/a.xml https://cdn.example.test/b.xml" {
+		t.Fatalf("configured = %v", got)
+	}
+}
diff --git a/classes/robots_value_test.go b/classes/robots_value_test.go
new file mode 100644
index 0000000..9725f6c
--- /dev/null
+++ b/classes/robots_value_test.go
@@ -0,0 +1,133 @@
+package classes
+
+import (
+	"errors"
+	"math/rand"
+	"strings"
+	"testing"
+)
+
+// robotsCombinations enumerates every combination of the C5 grammar's
+// directives (with representative arguments).
+func robotsCombinations() []Robots {
+	ptr := func(n int) *int { return &n }
+	var out []Robots
+	for _, index := range []string{"", "index", "noindex"} {
+		for _, follow := range []string{"", "follow", "nofollow"} {
+			for flags := 0; flags < 8; flags++ {
+				for _, snippet := range []*int{nil, ptr(-1), ptr(0), ptr(160)} {
+					for _, image := range []string{"", "none", "standard", "large"} {
+						for _, video := range []*int{nil, ptr(-1), ptr(30)} {
+							for _, after := range []string{"", "2027-01-31"} {
+								out = append(out, Robots{
+									Index: index, Follow: follow,
+									NoArchive: flags&1 != 0, NoSnippet: flags&2 != 0, NoImageIndex: flags&4 != 0,
+									MaxSnippet: snippet, MaxImagePreview: image, MaxVideoPreview: video,
+									UnavailableAfter: after,
+								})
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+	return out
+}
+
+func TestRobotsValueRoundTrip(t *testing.T) {
+	rng := rand.New(rand.NewSource(32))
+	combos := robotsCombinations()
+	if len(combos) != 3*3*8*4*4*3*2 {
+		t.Fatalf("%d combinations", len(combos))
+	}
+	for _, want := range combos {
+		value := want.String()
+		got, err := ParseRobots(value)
+		if err != nil {
+			t.Fatalf("ParseRobots(%q): %v", value, err)
+		}
+		if got.String() != value {
+			t.Fatalf("round trip %q -> %q", value, got.String())
+		}
+		if got.Header() != strings.ReplaceAll(value, ",", ", ") {
+			t.Fatalf("Header(%q) = %q", value, got.Header())
+		}
+		if got.Empty() != (value == "") {
+			t.Fatalf("Empty(%q) = %v", value, got.Empty())
+		}
+		// Any order, spaces and case read the same value back in the
+		// fixed order.
+		parts := strings.Split(value, ",")
+		rng.Shuffle(len(parts), func(i, j int) { parts[i], parts[j] = parts[j], parts[i] })
+		for i := range parts {
+			if i%2 == 0 {
+				parts[i] = " " + strings.ToUpper(parts[i]) + " "
+			}
+		}
+		if value != "" {
+			norm, err := NormalizeRobots(strings.Join(parts, ","))
+			if err != nil || norm != value {
+				t.Fatalf("NormalizeRobots(%q) = %q, %v; want %q", strings.Join(parts, ","), norm, err, value)
+			}
+		}
+	}
+}
+
+func TestRobotsValueAllInheritIsEmpty(t *testing.T) {
+	for _, value := range []string{"", "   ", "\t"} {
+		r, err := ParseRobots(value)
+		if err != nil || !r.Empty() || r.String() != "" {
+			t.Fatalf("ParseRobots(%q) = %+v, %v", value, r, err)
+		}
+	}
+	if s := (Robots{}).String(); s != "" {
+		t.Fatalf("all-inherit serialises to %q", s)
+	}
+}
+
+func TestRobotsValueMalformed(t *testing.T) {
+	for _, value := range []string{
+		",", "index,", ",noindex", "index,,follow",
+		"index,noindex", "follow,nofollow", "noindex,noindex", "noarchive,noarchive",
+		"max-snippet:1,max-snippet:2",
+		"index:1", "nofollow:yes", "noarchive:1",
+		"max-snippet", "max-snippet:", "max-snippet:abc", "max-snippet:-2", "max-snippet:1.5",
+		"max-video-preview", "max-video-preview:-5",
+		"max-image-preview", "max-image-preview:huge", "max-image-preview:",
+		"unavailable_after", "unavailable_after:2027-13-01", "unavailable_after:2027-02-30",
+		"unavailable_after:27-01-01", "unavailable_after:2027-1-1",
+		"none", "all", "noodp", "indexx",
+	} {
+		if _, err := ParseRobots(value); !errors.Is(err, ErrRobotsValue) {
+			t.Errorf("ParseRobots(%q) = %v, want ErrRobotsValue", value, err)
+		}
+		if _, err := NormalizeRobots(value); err == nil {
+			t.Errorf("NormalizeRobots(%q) accepted", value)
+		}
+	}
+}
+
+func TestRobotsValueInherit(t *testing.T) {
+	parse := func(v string) Robots {
+		t.Helper()
+		r, err := ParseRobots(v)
+		if err != nil {
+			t.Fatal(err)
+		}
+		return r
+	}
+	for _, tc := range []struct{ upper, lower, want string }{
+		{"", "", ""},
+		{"noindex", "index,nofollow", "noindex,nofollow"},
+		{"", "noindex,follow", "noindex,follow"},
+		{"index,follow", "noindex,nofollow,noarchive", "index,follow,noarchive"},
+		{"max-snippet:10", "max-snippet:50,max-image-preview:large", "max-snippet:10,max-image-preview:large"},
+		{"unavailable_after:2027-01-01", "unavailable_after:2028-01-01,max-video-preview:5", "max-video-preview:5,unavailable_after:2027-01-01"},
+		{"nosnippet", "noimageindex", "nosnippet,noimageindex"},
+	} {
+		if got := parse(tc.upper).Inherit(parse(tc.lower)).String(); got != tc.want {
+			t.Errorf("%q over %q = %q, want %q", tc.upper, tc.lower, got, tc.want)
+		}
+	}
+}
diff --git a/classes/templates_test.go b/classes/templates_test.go
new file mode 100644
index 0000000..16e74b4
--- /dev/null
+++ b/classes/templates_test.go
@@ -0,0 +1,75 @@
+package classes
+
+import (
+	"testing"
+
+	"git.golem15.com/golem15/sm-seo-plugin/models"
+)
+
+// TestTemplates: rendering fills the three placeholders, collapses spaces
+// and trims separators an empty placeholder leaves; an unknown placeholder
+// is refused when the template is saved.
+func TestTemplates(t *testing.T) {
+	vars := TemplateVars{Title: "Grzyby leśne", Description: "O grzybach", Site: "Atlas"}
+	for _, tc := range []struct {
+		name, tpl string
+		vars      TemplateVars
+		want      string
+	}{
+		{"title and site", "%title% | %site%", vars, "Grzyby leśne | Atlas"},
+		{"description", "%description% – %site%", vars, "O grzybach – Atlas"},
+		{"every placeholder twice", "%title% %title% %site%", vars, "Grzyby leśne Grzyby leśne Atlas"},
+		{"an empty site leaves no separator", "%title% | %site%", TemplateVars{Title: "About"}, "About"},
+		{"an empty title leaves no separator", "%title% · %site%", TemplateVars{Site: "Atlas"}, "Atlas"},
+		{"separators of every kind are trimmed", "%title% — : , %site%", TemplateVars{Title: "X"}, "X"},
+		{"inner separators stay", "%title% | Blog | %site%", TemplateVars{Title: "X", Site: "Y"}, "X | Blog | Y"},
+		{"runs of spaces collapse", "  %title%   \t  %site%  ", vars, "Grzyby leśne Atlas"},
+		{"an empty template renders nothing", "", vars, ""},
+		{"a blank template renders nothing", "   ", vars, ""},
+		{"text without placeholders", "Static title", vars, "Static title"},
+		{"an unknown placeholder renders as written", "%title% %author%", vars, "Grzyby leśne %author%"},
+		{"everything empty", "%title% | %site%", TemplateVars{}, ""},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := RenderTemplate(tc.tpl, tc.vars); got != tc.want {
+				t.Fatalf("RenderTemplate(%q) = %q, want %q", tc.tpl, got, tc.want)
+			}
+		})
+	}
+
+	for _, tc := range []struct {
+		tpl, unknown string
+	}{
+		{"%title% | %site%", ""},
+		{"%description%", ""},
+		{"", ""},
+		{"100% sure", ""},
+		{"%author% | %site%", "%author%"},
+		{"%title% %Title%", "%Title%"},
+		{"%%", "%%"},
+		{"%site_name%", "%site_name%"},
+		{"%title% %date% %page%", "%date%"},
+	} {
+		if got := models.UnknownPlaceholder(tc.tpl); got != tc.unknown {
+			t.Errorf("UnknownPlaceholder(%q) = %q, want %q", tc.tpl, got, tc.unknown)
+		}
+		problems := models.TemplateProblems(tc.tpl)
+		if tc.unknown == "" && problems != nil {
+			t.Errorf("TemplateProblems(%q) = %+v", tc.tpl, problems)
+		}
+		if tc.unknown != "" && (len(problems) != 1 || problems[0].Key != "golem15.seo::lang.settings.template_unknown" || problems[0].Params["placeholder"] != tc.unknown) {
+			t.Errorf("TemplateProblems(%q) = %+v", tc.tpl, problems)
+		}
+	}
+
+	refused := models.Settings{TitleTemplate: "%title% | %brand%", HomeTemplate: "%site% %x%"}.Problems()
+	if len(refused["title_template"]) != 1 || len(refused["home_template"]) != 1 {
+		t.Fatalf("settings problems = %+v", refused)
+	}
+	if ok := (models.Settings{TitleTemplate: "%title% | %site%", HomeTemplate: "%site%"}).Problems(); len(ok) != 0 {
+		t.Fatalf("valid templates refused: %+v", ok)
+	}
+	if len(models.KnownPlaceholders) != 3 || PlaceholderTitle != models.KnownPlaceholders[0] || PlaceholderDescription != models.KnownPlaceholders[1] || PlaceholderSite != models.KnownPlaceholders[2] {
+		t.Fatalf("the rendered and the validated placeholders differ: %v", models.KnownPlaceholders)
+	}
+}
diff --git a/go.mod b/go.mod
index 0d3ff9b..6c1a05c 100644
--- a/go.mod
+++ b/go.mod
@@ -11,6 +11,7 @@ require (
 	github.com/testcontainers/testcontainers-go v0.44.0
 	github.com/testcontainers/testcontainers-go/modules/postgres v0.44.0
 	gocloud.dev v0.46.0
+	gorm.io/driver/postgres v1.6.3
 	gorm.io/gorm v1.31.2
 )
 
@@ -178,7 +179,6 @@ require (
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20260316180232-0b37fe3546d5 // indirect
 	google.golang.org/grpc v1.79.3 // indirect
 	google.golang.org/protobuf v1.36.11 // indirect
-	gorm.io/driver/postgres v1.6.3 // indirect
 )
 
 replace git.golem15.com/golem15/summercms => ../summercms.go